1. Field of the Invention
The present invention relates to a digital data recording apparatus which performs digital encoding compression on various information signals and records the encoding compressed data on a non-volatile semiconductor memory card, and more particularly, to a digital data recording apparatus which is capable of consecutively recording, without lack of information data, information data such as a moving image or sound which progresses in a time series manner, in empty data areas which discontinuously exist in the non-volatile memory card.
2. Description of the Related Art
In recent years, the recording capacities of non-volatile semiconductor memories have been increasing and the recordable amount of data per non-volatile semiconductor memory has been increasing. Non-volatile semiconductor memories having card-like shapes have been developed, and digital still cameras for recording still images and audio recording equipment which use such cards in place of silver-halide film or audio recording magnetic tape have been developed and put into practice.
This type of digital still camera and audio recording equipment converts an analog signal picked up and generated by a photographic camera or a microphone into a digital signal, performs encoding compression on the digital signal to convert the digital signal into data having a predetermined data format, and records the data on the non-volatile semiconductor memory. The non-volatile semiconductor memory has a data storage area divided into plural physical blocks each of which stores a predetermined amount of data, and is capable of managing recording or erasure of data for each of the physical blocks. In general, in order to enable recorded data to be read and edited on computer equipment, the non-volatile semiconductor memory adopts a data format conforming to MS-DOS which is an OS for computer equipment.
A microprocessor converts the encoding compressed recording data into the data format of MS-DOS and creates management file data relative to the recorded data, and records the encoding compressed recorded data on physical blocks of the non-volatile semiconductor memory. Thus, reading and erasure of data recorded on plural physical blocks are performed by using the file management data.
A specific example of a digital data recording apparatus using the non-volatile semiconductor memory will be described below with reference to FIGS. 10 and 11. FIG. 10 is a block diagram showing the construction of an audio digital data recording/reproducing apparatus, and FIG. 11 is an explanatory view showing the configuration of physical blocks of the non-volatile semiconductor memory.
An audio input circuit 21 of the audio digital data recording/reproducing apparatus 20 shown in FIG. 10 is made of a microphone (not shown) which picks up sound such as music or human voice and generates an analog electrical signal, and an amplifier circuit (not shown) which amplifies the analog electrical signal generated by the microphone.
During recording, the analog audio signal generated by the audio input circuit 21 is converted to a digital audio signal by an analog/digital conversion circuit (hereinafter referred to as the A/D circuit) 22, and the digital audio signal is supplied to an encoding compression circuit 23. The encoding compression circuit 23 performs encoding compression on the digital audio signal, thereby generating predetermined digital compressed data. The encoding compression in the encoding compression circuit 23 uses the compression technique of G729A which is an ITU (the International Telecommunications Union) standard. The digital encoding compressed data generated by the encoding compression circuit 23 is recorded on a card provided with a non-volatile semiconductor memory (hereinafter referred to as the non-volatile memory card) 25, via a control means 24 composed of a microprocessor (MPU). As is well known, the microprocessor is also called CPU, and is made of one chip on which are integrated various units such as an arithmetic unit which performs arithmetic and logic operations, a control unit which performs interpretations of instructions and generation of control signals, and a storage unit. The control means 24 exerts control on writing and reading of the digital encoding compressed data to and from the non-volatile memory card 25, and also generates management data on the written digital encoding compressed data.
During reproduction, the digital encoding compressed data read from the non-volatile memory card 25 under the control of the control means 24 is expanded and decoded by a decoding expansion circuit 26, whereby the digital encoding compressed data is converted to a digital audio signal. The digital audio signal generated by the decoding expansion circuit 26 is converted to an analog audio signal by a digital/analog conversion circuit (hereinafter referred to as the D/A circuit) 27, and the analog audio signal is supplied to an audio output circuit 28 made of an amplifier circuit and a speaker (none of which is shown).
An operating switch 29 and a liquid crystal display 30 are connected to the control means 24. The operating switch 29 serves as an operating input means which has a switch for entering an operation input, such as audio recording, audio reproduction or power-off, into the audio digital data recording/reproducing apparatus 20. The liquid crystal display 30 displays the operating state of the audio digital data recording/reproducing apparatus 20 according to the input form the operating switch 29.
Incidentally, the non-volatile memory card 25 is capable of being removably fitted into a card slot provided in the body (not shown) of the audio digital data recording/reproducing apparatus 20.
The A/D circuit 22, the encoding compression circuit 23, the decoding expansion circuit 26 and the D/A circuit 27 are formed as a one-chip audio processing integrated circuit (hereinafter referred to as the audio processing IC).
The recording state of the digital encoding compressed data to be recorded on the non-volatile memory card 25 of the audio digital data recording/reproducing apparatus 20 having the above-described construction will be described below with reference to FIG. 11.
If the non-volatile semiconductor memory used in the non-volatile memory card 25 has a recording capacity of, for example, 8 Mbytes, the data recording area of the non-volatile semiconductor memory is managed in the state of being divided into 1,024 physical blocks. The state of the physical blocks is schematically shown in FIG. 11.
Assuming that data are already recorded on physical blocks 0 to 2, physical blocks 4 and 5 and physical blocks 8 to 1014 in the non-volatile memory card 25, if new digital encoding compressed data are to be recorded, the physical blocks are searched in order from physical block 0 and the new digital encoding compressed data are sequentially recorded on unrecorded physical blocks. In this case, the shown physical blocks 3, 6 and 7 are immediately detected by search, but it takes time to detect an unrecorded physical block such as physical block 1015 located near the bottom.
In a digital data recording apparatus provided with the non-volatile memory card 25, during recording of digital data such as sound or a moving image which progresses in a time series manner, even while an unrecorded physical block is being searched for in the non-volatile memory card 25, the data progresses, so that there is a possibility that when the data is recorded after an unrecorded physical block has been detected, the data which has progressed during the search may be lost.
Incidentally, each of the clusters shown in FIG. 11 is a logical minimum unit of a file managed by the FAT (File Allocation Table) file system of MS-DOS which will be described later, and the respective clusters are present to correspond to the physical blocks.
As described above, in the related art, when digital data compressed by digital encoding on the basis of information which continuously progresses in a time series manner is to be newly recorded on the non-volatile memory card, an unrecorded physical block of the non-volatile memory card is searched for, and each time an unrecorded physical block is discovered, the digital encoding compressed data is recorded. This leads to the problem that even while the unrecorded physical block is being searched for, the digital encoding compressed data to be newly recorded progresses, and when the unrecorded physical block is discovered and recording of the digital encoding compressed data is started, data which progresses during the search for the unrecorded physical block will be lost.
The invention provides a digital data recording apparatus which, when recording of new digital data on a non-volatile memory card, is capable of quickly searching for an unrecorded physical block and recording the new digital data on the unrecorded physical block without lack of digital data.
According to the invention, a digital data recording apparatus comprises: a digital encoding compression means for converting analog information which progresses in a time series manner into digital encoding compressed data; an empty area detection means for detecting an unrecorded empty area of a non-volatile memory card which records in predetermined units of blocks the digital encoding compressed data converted by the digital encoding compression means; a storage means for storing in advance information on an empty area of the non-volatile memory card detected by the empty area detection means; and a recording control means for executing control to record the digital encoding compressed data on the empty area of the non-volatile memory card on the basis of the information on the empty area stored in the storage means, and generating recording data containing management data on the digital encoding compressed data.
In the digital data recording apparatus, an unrecorded empty area of the non-volatile memory card is searched for and the detected empty area information is stored in the storage means in advance in preparation for recording. During recording, since the digital encoding compressed data is recorded in an empty area of the non-volatile memory card on the basis of the empty area information stored in the storage means in advance, it is possible to quickly search for an unrecorded physical block of the non-volatile memory card and record new digital data on the unrecorded physical block. Since a search for the unrecorded physical block is quickly performed, lack of digital data can be prevented from occurring in digital data to be recorded.
According to the invention, in the digital data recording apparatus, the empty area detection means searches through recording areas of the non-volatile memory card from a leading location to a terminal location and stores detected empty area information by continuously pushing the detected empty area information onto a stack of the storage means in search order. The recording control means executes control to start recording from a recording area which corresponds to final empty area information stored on the stack of the storage means, when the recording control means is to record new digital encoding compressed data on the non-volatile memory card.
According to the invention, in the digital data recording apparatus, the empty area detection means searches through recording areas of the non-volatile memory card from a terminal location to a leading location and stores detected empty area information by continuously pushing the detected empty area information onto a stack of the storage means in search order. The recording control means executes control to start recording from a recording area which corresponds to final empty area information stored on the stack of the storage means, when the recording control means is to record new digital encoding compressed data on the non-volatile memory card.
According to the invention, the digital data recording apparatus further comprises a memory card fitting detection means for detecting whether the non-volatile memory card has been fitted into a body of the digital data recording apparatus, and the non-volatile memory card is removably provided in the body of the digital data recording apparatus, and the empty area detection means executes a search for an empty area of the non-volatile memory card when the memory card fitting detection means detects that the non-volatile memory card has been fitted.
In the above-described digital data recording apparatus, when the memory card fitting detection means provided in a card slot device of the body of the digital data recording apparatus detects that the non-volatile memory card has been fitted, the empty area detection means executes a search for an empty area of the non-volatile memory card. Accordingly, when the non-volatile memory card is fitted, empty area information can be automatically stored in the storage means.
According to the invention, the digital data recording apparatus further comprises an input means for setting an operating mode of the body of the digital data recording apparatus, and the empty area detection means executes a search for an empty area of the non-volatile memory card when the input means is operated.
In the above-described digital data recording apparatus, after the non-volatile memory card has been fitted into the body of the digital data recording apparatus, a search for an empty area of the non-volatile memory card is executed when any key of the operation input means, for example, a reproducing switch is operated. Accordingly, as long as the non-volatile memory card is fitted, a user can at will execute a search for an empty area at any time.
According to the invention, the digital data recording apparatus further comprises a remaining capacity calculation means for finding a total empty area quantity on the basis of empty area information stored by being pushed onto a stack of the storage meansand calculates a recordable time from the total empty area quantity and a recording time per unit empty area.
In the above-described digital data recording apparatus, since the total empty area quantity is found on the basis of the empty area information stored in the storage means and the remaining recording time is calculated on the basis of the total empty area quantity, it is possible to quickly calculate and display the remaining capacity.
According to the invention, in the digital data recording apparatus, when empty area information detected by the empty area detection means is to be stored by being pushed onto a stack of the storage means, a first detected empty area is stored by being pushed onto the bottom of the stack of the storage means in accordance with a logical initial value corresponding to a value indicative of a maximum recording area quantity of the non-volatile memory card, and the empty area information is assigned a logical number obtained by decrementing the logical initial value by one in units of empty areas each time the empty area information is pushed, recording being executed in order from the top of empty areas pushed in the stack of the storage means when new digital encoding compressed data is being recorded on the non-volatile memory card.